Direct light transmittance through ceramic brackets.

The objective of this study was to investigate the degree of direct light transmittance (%T) of various types of esthetic brackets and to correlate these values with their structure, morphologic factors, and composition. Eight types of brackets were used in the study; six brackets of each type were tested. An ultraviolet-visible spectroscopic direct transmission analysis was performed at 320 to 700 nm wavelength range. From each spectrum, the %T corresponded to the peak absorbance wavelength of the photoinitiator of the polymerization was recorded (468 nm). Recorded data were analyzed with one-way analysis of variance and Scheffe's test at alpha = 0.05 significance level. In addition, scanning electron microscope (SEM) images were used to reveal the structure and morphologic factors of the brackets tested. Highest %T values (Mean +/- 1 SD) were obtained from a monocrystal type of bracket (Starfire ["A" Company, San Diego, Calif.] 35.02 +/- 1.59%), followed by a polycrystalline (Fascination [Dentaurum, Pforzhein, Germany] 5.70 +/- 1.41%) and a ceramic/polycarbonate base one (Ceramaflex [TP Orthodontics, Inc., La Porte, Ind.] 4.02 +/- 0.96%). Also other brands presented the following data: Allure (GAC, Central Islip, N.Y.) 3.62 +/- 0.5%; Transcend 2000 (Unitek/3M, Monrovia, Calif.) 2.62 +/- 0.5%; Fascination (edgewise) (Dentaurum, Pforzhein, Germany) 1.97 +/- 0.69%; Lumina (Ormco, Glendora, Calif.) 1.57 +/- 0.5%; Signature (RMO, Denver, Colo.) 1.22 +/- 0.5%. The results showed that the structure, morphologic factors, and composition of the brackets tested were found to affect direct light transmission significantly.(ABSTRACT TRUNCATED AT 250 WORDS)